1. Field of the Invention
The invention relates to an apparatus for forming a number of sync blocks to recording and reproducing digital data.
2. Related Background Art
Hitherto, a DV (Digital Video) format specified by the HD Digital VCR Council has been known as a system for recording video data onto a magnetic tape. According to the DV format, as shown in FIG. 5A, digital data is recorded by forming a number of helical tracks onto a tape T. As shown in FIG. 5B, each track is constructed by an ITI (Insert and Track Information) sector, an audio sector, a video sector, and a subcode sector. A rotary head records the data into each sector while tracing the track in the direction shown by an arrow A. At this time, a plurality of sync blocks are formed by adding a predetermined sync pattern to a predetermined amount of the digital data, and the data is recorded into each sector on a sync block unit basis. Gaps are formed between the ITI sector and the audio sector, between the audio sector and the video sector, and between the video sector and the subcode sector, respectively.
According to the DV format, as mentioned above, since a plurality of gaps are formed and a preamble and a postamble are further formed in each sector, there is a problem such that a recording rate of the substantial data cannot be sufficiently obtained. As a method of solving such a problem, a method whereby no gap is provided for each track but a conventional gap area is used as a data area has been disclosed in Japanese Patent Application Laid-Open No. 2000-270576.
Further, a method whereby the ITI sector is constructed only by the preamble, thereby widening the data area more, has also been disclosed in Japanese Patent Application Laid-Open No. 2001-275077. A format according to such a method is referred to as an “HD format” hereinbelow. A construction of one track in the HD format is shown in FIG. 5C.
When the data recorded as mentioned above is reproduced, it is necessary to detect whether the data recorded on the tape is the data in the HD format or the data in the DV format, to switch a process for the data. Therefore, in the apparatus disclosed in the above Official Gazette, the DV format is detected by detecting APT2, APT1, and APT0 data recorded in the ITI sector while the HD format is detected by detecting an ID of a main sector or an ID of the subcode sector.
However, according to such a method, it is necessary to reproduce the data in different portions on the tracks recorded on the magnetic tape and discriminate an encoding method of the recorded data. There is, consequently, a problem such that complicated processes are required to discriminate the encoding method.